Fluidized development of electrostatic images

ABSTRACT

Development of a latent electrostatic image is effected by vibrating a mass of two-component developer on a support surface to maintain the developer mass in a fluidized state in close proximity to a latent electrostatic image bearing surface whereby toner is attracted to image areas to effect development thereof. The toner is replenished by passing toner from a suitable toner supply, such as a toner powder cloud, through apertures in the supporting surface which are larger than the toner particles and smaller than the carrier particles, whereby an adequate toner supply is maintained in the development zone without recirculating the carrier.

United States Patent Yang [54] FLUIDIZED DEVELOPMENT OF ELECTROSTATIC IMAGES [72] Inventor: Frank Y. Yang, Webster, NY.

[7 3] Assignee: Xerox Corporation, Stamford, Conn. [22] Filed: Sept. 17, 1970 [2]] Appl. No.: 72,997

[52] U.S. Cl. ..ll8/637,l17/l7.5,ll8/DIG.5 [51] Int. Cl. ..G03g 13/00 [58] Field ofSearch ..l18/637,DlG.5;ll7/17.5

[5 6] References Cited UNITED STATES PATENTS 3,396,700 8/1968 Donalies ..1 18/637 3,484,265 12/1969 Swyler ..1l7/17.5 3,393,663 7/1968 Donalies ..1 18/637 3,382,360 5/1968 Young et al. ..1 18/637 1151 3,654,900 1451 Apr. 11,1972

Primary Examiner-Mervin Stein Assistant ExaminerLeo Millstein Attorney-James J. Ralabate, Mam and Jangarathis, Michael J. Colitz, Jr. and Robert W. Mulcahy [57] ABSTRACT Development of a latent electrostatic image is effected by vibrating a mass of two-component developer on a support surface to maintain the developer mass in a fluidized state in close proximity to a latent electrostatic image bearing surface whereby toner is attracted to image areas to effect development thereof. The toner is replenished by passing toner from a suitable toner supply, such as a toner powder cloud, through apertures in the supporting surface which are larger than the toner particles and smaller than the carrier particles, whereby an adequate toner supply is maintained in the development zone without recirculating the carrier.

14 Claims, 3 Drawing Figures PATENTED PR 1 1 1912 3.654800 SHEET 1 OF 2 Powder 83 88 6/ Cloud 7 Supply Fig. l.

lN-VEN'I'OR.

Frunk Y. Yang ATTORNEYS PATENTEDAPR 11 I972 23. 654.900

sum 2 or 2 l NVE N TOR.

Frdnk Y. Yang FLUIDIZED DEVELOPMENT OF ELECTROSTATIC IMAGES BACKGROUND OF THE INVENTION This invention relates to electrostatography and more particularly to the development of latent electrostatic images.

The most common electrostatographic process is of the electrophotographic type. In the practice of electrophotography, as described in U.S. Pat. No. 2,297,691, to Chester F. Carlson, an electrographic surface comprising a layer of photoconductive insulating material affixed to a conductive backing is used to support electrostatic images. In the usual method of carrying out the process, the electrographic plate is electrostatically charged uniformly over its surface and then exposed to a light pattern of the image being reproduced to thereby discharge the charge in the areas where light reaches the layer. The undischarged areas of the layer form an electrostatic charge pattern in conformity with the configuration of the original light pattern.

The latent electrostatic image can then be developed by contacting it with a finely divided electrostatically attractible material such as a resinous powder. The powder is held in image areas by the electrostatic charges on the layer. Where the charge is greatest, the greatest amount of material is deposited; and where the charge is least, little or no material is deposited. Thus, a powder image is produced in conformity with the light image of the copy being reproduced. The powder is subsequently transferred to a sheet of paper or other surface and suitably affixed to thereby form a permanent print.

The electrostatically attractable developing material commonly used in electrophotography consists of a pigmented resinous powder referred to here as toner" and a coarse granular material called carrier. The carrier is usually coated with a material removed in the triboelectric series from the toner so that a triboelectric charge is generated between the powder and the granular carrier. Such charge causes the powder to adhere to the carrier. The carrier also provides mechanical control so that the toner can be readily handled and brought into contact with the exposed electrophotographic surface. The powder particles are then attracted to the electrostatic image to produce a visible powder image on the electrophotographic surface.

The development of a latent electrostatic image by mechanically fluidizing a two-component developer is disclosed in U.S. Pat. No. 3,380,437 to Swyler and U.S. Pat. No. 3,393,663 to Donalies. As described in these patents, a mass of two-component developer of the type hereinabove described is vibrated beneath a latent electrostatic image bearing surface at a rate rapid enough to effect fluidization of the developer mass with the image being developed by the toner being drawn to the image areas. Each of the machines described in these patents provides for retoning of the carrier by a recirculation technique similar to the the technique employed for retoning carrier in a machine employing a cascade development technique; i.e., recirculating the carri er through a sump, from which the retoned carrier is conveyed to the developing zone. As a result of the necessity to continuously recirculate the developer carrier, the machines employing the fluidization technique have the same drawbacks as the machines employing the cascade development technique; i.e., the large area encompassed by the developer portion of the machine and the mechanical complexities associated with such recirculation. In addition, the carrier and unused toner particles which drop by gravity into the sump generate a cloud of toner particles which result in undesirable high background deposits of toner in non-image areas.

SUMMARY OF THE INVENTION An object of this invention is to provide for improved development of a latent electrostatic image.

Another object of this invention is to provide for improved development of a latent electrostatic image by a fluidization technique.

A further object of this invention is to provide for development of a latent electrostatic image by a fluidization technique which provides for improved retoning of the developer.

These and other objects of the invention should be more readily apparent from reading the following detailed description thereof with reference to the accompanying drawings.

The objects of this invention are broadly accomplished by developing a latent electrostatic image by a fluidization technique in which a mass of two-component developer comprised of a toner and carrier is supported on a surface positioned in proximity to a latent electrostatic image bearing surface and the surface is caused to move to effect fluidization of the developer massin proximity to the image bearing surface, with the toner being attracted toward the latent image areas to provide a visible image. The developer supporting surface is provided with a plurality of apertures which are large enough to permit toner to pass therethrough, and which are small enough to prevent the carrier from passing therethrough. The apertures are connected to a source of toner and the mass of developer on the supporting surface is retoned by supplying toner through the apertures, thereby eliminating the necessity to continuously recirculate the developer carrier in order to provide an adequate supply of toner in the development zone.

DESCRIPTION OF THE DRAWINGS DETAILED DESCRIPTION OF THE INVENTION Referring to FIG. 1 of the drawings, there is illustrated an electrostatographic machine employing one embodiment of this invention. The machine includes an image forming member such as, for example, an electrophotographic cylinder designated 10 and generally comprising a photoconductive insulating layer disposed on a conductive backing. The cylinder is rotatably mounted on a suitable axle II or other bearing member and is adapted to be rotated by drive means such as, for example, an electric motor (not shown) or the like. Preferably the cylinder, and in particular its conductive backing, is electrically grounded. The image forming or image receiving surface of the electrophotographic cylinder 10 is adapted to be rotated past appropriate electrophotographic processing stations disposed and positioned to form an electrostatic image on the cylinder surface. For example, when used with a photoconductive insulating electrophotographic image surface, the electrophotographic processing stations may include means for charging or sensitizing, exposure means, and cleaning means. Illustrated in the figure is a charging station generally designated 14 at which is positioned a corona discharge electrode 15, desirably one or more high voltage corona discharge wires 16 mounted within a grounded shield 17 and adapted to be connected to a high voltage source such as, for example, a positive polarity direct current source of several thousand volts. In general the voltage applied to the corona discharge electrode will be sufficient to cause air ionization surrounding the corona wires and it is understood that such a corona discharge potential is generally in the order of several thousand volts and usually 5 to l0 thousand volts as disclosed, for example, in Walkup U.S. Pat. No. 2,777,957.

Positioned next adjacent to the charging station is an exposure station generally designated 18 and including suitable means for projecting or otherwise directing a light or optical image onto the surface of the electrophotographic drum. The exposure station may include a slit projection mechanism for exposing onto the drum surface a moving projected image of microfilm or the like, and may include means for projecting onto the surface documentary of other information or an image corresponding to the face of a cathode ray tube or the like. As is disclosed in Carlson US. Pat. No. 2,297,691, the combination of electric field and exposure to activating radiation forms on the drum surface an electrostatic image capable of being developed or made visible by deposition of finely divided charged particles.

A development station for developing the latent electrostatic image, generally designated as 21, is positioned at a subsequent location around the circumference of the drum, the structure and operation of which is hereinafter described.

Positioned subsequently around the surface of the electrophotographic drum is an image transfer station generally designated 27 including for example a supply roll 28 of transfer material such as, for example, a roll of paper and a take-up roll 29 together with guide means and the like to feed the image transfer material into contiguous relationship with the electrophotographic drum. As illustrated in the figure, suitable guide rolls 30 may guide and optionally drive the transfer web into contact with the electrophotographic drum, and transfer means such as, for example, a corona discharge electrode 31 is positioned to transfer the developer image to the image web at the transfer station. Preferably, the transfer means is a corona discharge electrode of substantially the same construction as is located at the charging station 14 although other transfer means may be employed such as the means disclosed in U.S. Pat. No. 2,807,233. For the usual case of direct or positive-to-positive photographic copy the charging electrode 15 and the transfer electrode 31 are of the same polarity and for the opposite situation of photographic reversal the electrodes are of opposite polarity. Optionally positioned near the transfer station and along the line of travel of the transfer web subsequent to the transfer station is a fusing station generally designated 32 and including a plurality of heating elements 33 suitably contained within a housing 34 and adapted to fuse onto the web surface the image that has been transferred thereto. It is understood that suitable vapor fixing means may be employed as disclosed for example in Carlson US. Pat. No. 2,776,907.

Disposed next adjacent to the transfer station and between the transfer station and the charging station is a cleaning station generally designated 36 and comprising for example a cloth or, preferably, rotatable brush 37 operated by suitable drive means to brush against the electrophotographic drum surface and remove residual powder therefrom. Suitable brush cleaning apparatus is illustrated in Turner et al. US. Pat. No. 2,751,616.

The development station 21 includes a developer container 51 comprised of spaced end plates 52 each of which is apertured at 53; a lower arcuate tray or plate 54 connected to the end plates 52; an intermediate arcuate plate or tray 55 connected to the end plate 52 concentric with and of greater length than the lower plate 54, and spaced interior side plates 56 connected between the intermediate plate 55 and lower plate 54 and to the end plates 52. The end plates 52, side plates 56, lower plate 54 and intermediate plate 55 defining a compartment or housing 57 for distributing toner to the surface of plate 55, as hereinafter described.

The developer container 51 is mounted for oscillating motion about the shaft 11 of drum with the intermediate plate 55 being concentric with and in close proximity to the circumferential surface of the drum 10 with the mounting being effected by mounting the end plates 52 at opposite faces of the drum 10 on the shaft 11 through apertures 53 in a manner such that the container 51 is free to oscillate about the shaft 1 1.

The intermediate plate 55 supports a two-component developer comprised of toner and carrier of a type known in the art and is provided with a plurality of spaced apertures 58 over the surface thereof of a size large enough to permit the finely divided toner to pass therethrough and small enough to prevent the carrier from passing therethrough. The toner materials generally have an average particle size from 1 to 30 microns and the carrier generally has an average particle size of from 100 to 800 microns and, therefore, the size of the selected to permit toner to pass therethrough and prevent carrier from passing therethrough. The intermediate plate 55 extends about the circumference of the drum 18 over a length sufficient to prevent developer material which is supported thereon from being carried off of the plate 55 and, therefore, a portion of the upper surface of plate 55 is free of apertures and acts as a seal and experiences little or no developer flow, generally the portions of the plate 55 which extend beyond the outer extremities of the lower plate 54. A suitable seal which provides sealing contact between the plate 55 and the drum 10 may be provided at either or both ends of the plate 55 for preventing developer material from being carried out of the developer container 51, but in general such sealing contact is not preferred.

The lower plate 54 is provided with an inlet aperture 59 which is connected to a powder cloud supply of toner, schematically indicated as 61, such as, for example, an aerosol type of supply, through a flexible conduit 62 for introducing toner material into the compartment 57 and then onto the surface of tray 55 through the apertures 58. The powder cloud supply is preferably provided with suitable means (not shown), such as a solenoid actuated device, for periodically and automatically supplying toner therefrom. The frequency of supply is adjustable in order to permit a machine user to control the amount of toner in the system in accordance with the type of image to be copied.

A series of development electrode wires 72 also span the two end plates 52, and are also concentrically oriented with respect to the drum 10 and arcuate plate 55. The spacing between the wires is such that developer may easily pass therethrough. These electrode wires are secured in the end plates by cutout section 73 in the end plates and are mounted through insulating strip barriers 74 of polyurethane foam or the like. The electrode wires are then either electrically connected to a source of potential (not shown) or a ground for the establishment of an electric field adjacent the drum. In addition to providing an electrode field adjacent the drum, the wires also act when oscillated with the end plate to vibrate the developer in the development zone and thereby aid in main taining the developer as a fluidized mass.

An oscillatory motion is imparted to the development container 51, including end plate 52, arcuate plate 55, and electrode wires 72 by any convenient motion producing assembly. One such assembly as illustrated herein includes a linkage arm 81 formed with an integral bearing 82 and 83 at each end. The first bearing 82 is pivotally mounted on a stud 8 formed exteriorly on one of the end plates. The second bearing 83 is pivotally mounted on a similar stud 87, formed on a slightly off center portion of a motor means 88. As such, on rotation of the motor means, reciprocation is imparted to the linkage arms 81 and end plate 52. The end plates, by reason of their mounting on the main drive shaft 11, are thus oscillated concentric with the drum. This oscillation is so rapid that the mass of two-component developer located between the drum and arcuate plate 55 suspends itself in a fluidized mass or bed due to the vibration imparted by the oscillating electrode wires and arcuate plate. This fluidized mass or bed will move into contact with the image on the drum.

in operation, the two-component developer material, comprised of toner and carrier, on the upper surface of plate 55 is fluidized by the oscillating motion of the developer container 51 and this fluidized developer moves into contact with the drum 10 which is rotated through the fluidized mass of developer on and between plate 55 and drum 10 to develop the latent image previously formed on drum 10. The toner material expended during such development is replenished from the powder cloud supply 61 which feeds additional toner material into compartment 57 and then onto the tray 55 through the apertures 58 therein. A uniform mixing of toner and carrier is easily attained as a result of the fluidized state of the developer mass. In this manner, there is no necessity to continuously recirculate the carrier in order to maintain an adequate toner supply in the development zone.

apertures may be readily Another embodiment of the invention is illustrated in FIGS. 2 and 3 of the drawings which is similar to the embodiment illustrated in FIG. 1, except for the development station, with like parts being designated with like prime numerals. The embodiment of FIGS. 2 and 3 will therefore be described only with reference to the development station.

The development station 21' includes a development container 101 which is comprised of spaced arcuate end plates 102; a lower arcuate tray or plate 103 connected to the end plates 102; an intermediate arcuate plate or tray 104 connected to the end plates 102 concentric with and of greater length than the lower plate 103; and spaced interior side plates 105 connected between the intermediate plate 104 and lower plate 103 and to the end plates 102; the end plates 102, side plates 105, the lower plate 103 and intermediate plate 104 defining a compartment or housing 106 for distributing toner onto the surface of plate 104.

An arcuate vibrating screen 107 is mounted between the end plates 102 concentric with and above the intermediate plate 104 through a suitable insulating barrier 108, such as polyethylene foam or the like. The screen 107 is grounded or provided with a bias and thereby functions as a development electrode for establishing an electric field adjacent an image being passed through the development station. The screen 107 is of a length equal to the lower plate 103 in that the portion of the intermediate plate 104 which extends beyond the extremities of the plate 103, as hereinafter described, is not generally within the development area of the drum The apertures of the screen 107 are generally of a size such that the carrier including the toner can pass therethrough to develop the latent image on the surface of drum 10'.

The end plates 102 are each provided at each end with guide pins 111 which are mounted in apertures 112 in spaced support plates 113 positioned at opposite faces of the drum 10. The developer container 101 is supported in the mounting plates 113 in a manner such that the intermediate arcuate plate 104 is concentric with and in close proximity to the drum 10' with the pins 111 positioned in the apertures 112 of mounting plates 113 guiding the developer housing 101 to permit reciprocal movement transverse to the drum 10' and restrain movement longitudinal to the drum 10.

The intermediate plate 104 supports a two-component developer comprised of toner and carrier of a type known in the art and is provided with a plurality of spaced apertures 114 over the surface thereof of a size large enough to permit the finely. divided toner to pass therethrough and small enough to prevent the carrier from passing therethrough. The inter mediate plate 104 extends about the circumference of the drum 10 over a length sufficient to prevent developer material which is supported thereon from being carried out of the container 101 and, therefore, a portion of the upper surface of plate 104 is free of apertures and acts as a seal and experiences little or no developer flow, generally the portions of the plate 104 which extend beyond the outer extremities of the lower plate 103. A suitable seal which provides sealing contact between the plate 104 and the drum 10' may be provided at either or both ends of the plate 104 for preventing developer material from being carried out of the developer container 101, but in general such sealing contact is not preferred.

The lower plate 103 is provided with an inlet aperture 115 which is connected to a powder cloud supply of toner, schematically indicated as 116, through a flexible conduit 117 for introducing toner material into the compartment 106 and then onto the surface of tray 104 through the apertures 114.

A reciprocating motion in a direction transverse to the drum 10' is imparted to the development container 101 by any convenient motion producing assembly. One assembly as illustrated herein, includes a motor 121 mounted adjacent to one of the mounting plates 113 having a rotating circular drive plate 122 connected thereto, with the drive plate 122 being operatively connected to one of the end plates 102 through a connecting rod 123, the connecting rod 123 being mounted eccentrically to the drive plate 122. Accordingly, operation of the motor 121 results in reciprocal movement of the developer compartment 101 in a direction transverse to the drum 10'.

In operation, the motor 121 is operated at a speed which reciprocates the developer housing 101 at a rate at which the vibratory motion imparted to the screen 107 and the intermediate plate 104 effects fluidization of the mass of two-com-.

ponent developer positioned on the intermediate plate 104. The fluidized developer moves into contact with the rotating drum 10' passed therethrough to develop the latent electrostatic image previously formed on drum 10', with the screen 107, during the development, functioning as a development electrode, as generally known in the art. The toner material expended during such development is replenished from the powder cloud supply 116, which feeds additional toner material into the compartment 106 and then onto the tray 1104 through the apertures 114 therein. In this manner, there is no necessity to continuously recirculate the carrier in order to provide additional toner.

Numerous modifications and variations of the hereinabove described embodimentsof the invention are possible within the spirit and scope of the invention. Thus, for example, the hereinabove described embodiments include either longitudinal or transverse movement of the developer supporting surface for effecting fluidization of the developer mass, and it is to be understood that such fluidization could also be effected by reciprocation of a developer supporting surface towards and away from the latent electrostatic image bearing surface, provided the supporting surface includes apertures for replenishing depleted toner, as hereinabove described.

As another modification, the use of a development electrode in the development zone may be omitted in which case the developer supporting surface would not include a screen or wires, as hereinabove described. It is to be understood, however, that the use of a development electrode, is preferred. It is further to be understood that a development electrode may be provided in a manner other than as particularly described.

As a further modification, the toner may be introduced onto the developer supporting surface through the apertures therein in a manner other than as described. Thus, for example, the apertures in the developer supporting surface could be connected directly to a source of toner through a plurality of flexible conduits in which case the compartment beneath the developer supporting surface would be eliminated. These and other methods for providing toner to the developer supporting surface through said apertures should be apparent to those skilled in the art.

The invention has been particularly described with reference to a latent electrostatic image bearing surface in the form of a drum, but it is to be understood that the teachings of the invention are equally applicable to developing latent electrostatic images on surfaces other than drums, such as for example, a continuous belt, a moving web, a sheet or other surfaces. Similarly, although the invention has been particularly described with respect to the development of latent electrostatic images forrned by an electrophotographic technique, the invention is equally applicable to the development of latent images formed in a manner other than by electrophotography; e.g., latent electrostatic images formed by a pulsing electrode as employed, for example, in electrostatic printing processes. In addition, although the invention has been described with reference to developing a latent image for ultimate transfer to a surface to be employed as a final copy, such development could also be effected directly on the surface to be employed as the final copy; e.g., the latent image may be formed and subsequently developed on treated paper of a type known in the art. Consequently, the present invention is not limited to any particular technique for forming a latent electrostatic image or to any particular surface on which the image is to be developed.

The above modifications and applications and others are deemed to be well within the scope of those skilled in the art from the teachings herein and therefore no further enumeration of such modifications and applications is deemed necessary for a full understanding of the invention.

The present invention is particularly advantageous in that the present invention incorporates all of the advantages of effecting development by a fluidization technique without incorporating the previous limitations resulting from the necessity to maintaining an adequate supply of toner in the development zone. Thus, the present invention in which an adequate toner supply is maintained in the development zone, without recirculating the carrier, results in a smaller and less complicated machine. In addition, the developing zone and machine is cleaner as a result of elimination of the continuous circulation of carrier through a supply of toner.

Numerous modifications and variations of the present in vention are possible in light of the above teachings and therefore within the scope of the appended claims the invention may be practiced in a manner other than as particularly described.

What is claimed is:

1. In an electrostatographic machine for providing a latent image particle a conduit latent image bearing surface and subsequently rendering the latent image visible with a two-component developer material comprised of a toner and carrier, said machine including a developer supporting surface for said two'component developer in proximity to said latent imagebearing surface and means operatively connected to said developer supporting surface to effect movement of said developer supporting surface and thereby maintain said twocomponent developer as a fluidized mass in proximity to said latent image bearing surface whereby toner is attracted toward the latent image bearing surface to render the latent image visible, the improvement comprising: said developer supporting surface including a plurality of apertures smaller than the particle size of said carrier and larger than the particle size of said toner, said supporting surface extending beyond the portions of the path of the movable latent image bearing surface over which development is effected for a length sufficient to prevent said two component developer from being carried E of said supporting surface, said supporting surface being free of apertures beyond said portions; and toner supply means connected to said apertures to pass toner through said apertures to replenish the carrier supported on said developer supporting surface with toner.

2. The electrostatographic machine as defined in Claim 1 wherein said toner supply means includes: a compartment for toner, said developer supporting surface including said plurality of apertures being a wall of said compartment, whereby said developer supporting surface is in fluid flow communication with the interior of said compartment through said apertures; a powder cloud storage means for toner; and conduit means connecting the interior of said compartment with said powder cloud storage means, whereby toner is supplied from said powder cloud storage means to said compartment and then through said apertures to the developer supporting surface.

3. The electrostatographic machine as defined in claim 2 and further comprising a development electrode positioned between the developer supporting surface and said latentimage bearing surface.

4. The electrostatographic machine as defined in Claim 3 wherein the means for effecting movement of said developer supporting surface effects movement thereof in a direction transverse to said latent image bearing surface and said development electrode comprises a screen.

5. The electrostatographic machine as defined in claim 3 wherein the means for effecting movement of said developer supporting surface effects movement thereof in a direction longitudinal to said latent image bearing surface and said development electrode comprises a plurality of spaced parallel wires mounted in a direction transverse to the latent image bearing surface.

6. In an electrostatographic machine for providing a latent electrostatic image on a latent image bearing surface and subsequently rendering the latent image visible with a two-component developer material comprised of a toner and carrier, said machine including a developer supporting surface for said two-component developer in proximity to said latent imagebearing surface and means operatively connected to said developer supporting surface to effect movement of said developer supporting surface and thereby maintain said twocomponent developer as a fluidized mass in proximity to said latent image bearing surface whereby toner is attracted toward the latent image bearing surface to render the latent image visible, the improvement comprising; said developer supporting surface including a plurality of apertures smaller than the particle size of said carrier and larger than the particle size of said toner; toner supply means connected to said apertures to pass toner through said apertures to replenish the carrier supported on said developer supporting surface with toner, said toner supply means comprising a compartment for toner, said developer supporting surface including said plurality of apertures being a wall of said compartment, whereby said developer supporting surface is in fluid flow communication with the interior of said compartment through said apertures; a powder cloud storage means for toner; and conduit means connecting the interior of said compartment with said powder cloud storage means, whereby toner is supplied from said powder storage means to said compartment and then through said apertures to the developer supporting surface.

'7. The electrostatographic machine as defined in claim s and further comprising a development electrode positioned between the developer supporting surface and said latentimage bearing surface.

8. The electrostatographic machine as defined in claim 7 wherein the means for effecting movement of said developer supporting surface elfects movement thereof in a direction transverse to said latent image bearing surface and said development electrode comprises a screen.

9. The electrostatographic machine as defined in claim '7 wherein the means for effecting movement of said developer supporting surface effects movement thereof in a direction longitudinal to said latent image bearing surface and said development electrode comprises a plurality of spaced parallel wires mounted in a direction transverse to the latent image bearing surface.

It). In an electrostatographic machine for developing a latent electrostatic image including a latent-image bearing surface on the surface of a rotatable drum, an arcuate developer supporting surface for a two-component developer comprised of a toner and carrier in proximity to the latent-image bearing surface of the rotatable drum, and means operatively connected to said developer supporting surface to effect movement of said developer supporting surface and thereby main tain said two-component developer as a fluidized mass in proximity to said latent-image bearing surface, whereby toner is attracted to the latent image bearing surface to effect development of the latent image, the improvement compris ing: said developer supporting surface including a plurality of apertures smaller than the particle size of said carrier and larger than the particle size of said toner, said supporting surface extending about the circumference of the drum beyond the portions of the path of the drum over which development is effected for a length sufficient to prevent said two component developer from being carried off of said supporting surface, said supporting surface being free of apertures beyond said portions; and toner supply means connected to said apertures to pass toner through said apertures to replenish the carrier supported on said developer supporting surface with toner.

Ill. The electrostatographic machine as defined in claim It) wherein said toner supply means includes: a compartment for toner, said developer supporting surface including said plurality of apertures being a wall of said compartment, whereby said developer supporting surface is in fluid flow communication with the interior of said compartment through said apertures; a powder cloud storage means for toner; and conduit means connecting the interior of said compartment with said powder cloud storage means, whereby toner is supplied from said powder cloud storage means to said compartment and then through said apertures to the developer supporting surface.

12. The electrostatographic machine as defined in claim 11 and further comprising a development electrode. positioned between the developer supporting surface and said latentimage bearing surface.

13. The electrostatographic machine as defined in claim 12 wherein the means for efi'ecting movement of said developer 0 lel wires mounted in a direction transverse to the latent image bearing surface.

UNKTED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 0 v Iiated April 11. 1972 Inventor(s) Frank Y. Yang It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 25, "image particle a conduit latent" should be -image on a movable latent-.

Column 10, line 4, "10" should be l2-,

Signed and sealed this 15th day of August 1972.

(SEAL) I Attest:

EDWARD I LFLETCHERJR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO'WSO H0459) uscoMM-oc cows-p59 n .5. GOVERNMENT PRINTING OFFICE: l. O-Ji-JJ UNITED STATES PATENT OFFICE QERTllFlCATE OF CGRRECTION Pat n N 3. 654. 900 bated April 11. 1972 Inventor(s) Frank Yang It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 7, line 25, "image particle a conduit latent" should be -image on a movable latent",

Column 10, line 4, "10" should be -l2-,

Signed and sealed this 15th day of August 1972.

(SEAL) I Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM PO-1050 (10-69) USCOM'WDC 5D376 p6g w u.s. sovnnnzm rnm'mgo orncs: I!" o-au-au 

2. The electrostatographic machine as defined in Claim 1 wherein said toner supply means includes: a compartment for toner, said developer supporting surface including said plurality of apertures being a wall of said compartment, whereby said developer supporting surface is in fluid flow communication with the interior of said compartment through said apertures; a powder cloud storage means for toner; and conduit means connecting the interior of said compartment with said powder cloud storage means, whereby toner is supplied from said powder cloud storage means to said compartment and then through said apertures to the developer supporting surface.
 3. The electrostatographic machine as defined in claim 2 and further comprising a development electrode positioned between the developer supporting surface and said latent-image bearing surface.
 4. The electrostatographic machine as defined in Claim 3 wherein the means for effecting movement of said developer supporting surface effects movement thereof in a direction transverse to said latent image bearing surface and said development electrode comprises a screen.
 5. The electrostatographic machine as defined in claim 3 wherein the means for effecting movement of said developer supporting surface effects movement thereof in a direction longitudinal to said latent image bearing surface and said development electrode comprises a plurality of spaced parallel wires mounted in a direction transverse to the latent image bearing surface.
 6. In an electrostatographic machine for providing a latent electrostatic image on a latent image bearing surface and subsequently rendering the latent image visible with a two-component developer material comprised of a toner and carrier, said machine including a developer supporting surface for said two-component developer in proximity to said latent image-bearing surface and means operatively connected to said developer supporting surface to effect movement of said developer supporting surface and thereby maintain said two-component developer as a fluidized mass in proximity to said latent image bearing surface whereby toner is attracted toward the latent image bearing surface to render the latent image visible, the improvement comprising; said developer supporting surface including a plurality of apertures smaller than the particle size of said carrier and larger than the particle size of said toner; toner supply means connected to said apertures to pass toner through said apertures to replenish the carrier supported on said developer supporting surface with toner, said toner supply means comprising a compartment for toner, said developer supporting surface including said plurality of apertures being a wall of said compartment, whereby said developer supporting surface is in fluid flow communication with the interior of said compartment through said apertures; a powder cloud storage means for toner; and conduit means connecting the interior of said compartment with said powder cloud sTorage means, whereby toner is supplied from said powder storage means to said compartment and then through said apertures to the developer supporting surface.
 7. The electrostatographic machine as defined in claim 6 and further comprising a development electrode positioned between the developer supporting surface and said latent-image bearing surface.
 8. The electrostatographic machine as defined in claim 7 wherein the means for effecting movement of said developer supporting surface effects movement thereof in a direction transverse to said latent image bearing surface and said development electrode comprises a screen.
 9. The electrostatographic machine as defined in claim 7 wherein the means for effecting movement of said developer supporting surface effects movement thereof in a direction longitudinal to said latent image bearing surface and said development electrode comprises a plurality of spaced parallel wires mounted in a direction transverse to the latent image bearing surface.
 10. In an electrostatographic machine for developing a latent electrostatic image including a latent-image bearing surface on the surface of a rotatable drum, an arcuate developer supporting surface for a two-component developer comprised of a toner and carrier in proximity to the latent-image bearing surface of the rotatable drum, and means operatively connected to said developer supporting surface to effect movement of said developer supporting surface and thereby maintain said two-component developer as a fluidized mass in proximity to said latent-image bearing surface, whereby toner is attracted to the latent image bearing surface to effect development of the latent image, the improvement comprising: said developer supporting surface including a plurality of apertures smaller than the particle size of said carrier and larger than the particle size of said toner, said supporting surface extending about the circumference of the drum beyond the portions of the path of the drum over which development is effected for a length sufficient to prevent said two component developer from being carried off of said supporting surface, said supporting surface being free of apertures beyond said portions; and toner supply means connected to said apertures to pass toner through said apertures to replenish the carrier supported on said developer supporting surface with toner.
 11. The electrostatographic machine as defined in claim 10 wherein said toner supply means includes: a compartment for toner, said developer supporting surface including said plurality of apertures being a wall of said compartment, whereby said developer supporting surface is in fluid flow communication with the interior of said compartment through said apertures; a powder cloud storage means for toner; and conduit means connecting the interior of said compartment with said powder cloud storage means, whereby toner is supplied from said powder cloud storage means to said compartment and then through said apertures to the developer supporting surface.
 12. The electrostatographic machine as defined in claim 11 and further comprising a development electrode positioned between the developer supporting surface and said latent-image bearing surface.
 13. The electrostatographic machine as defined in claim 12 wherein the means for effecting movement of said developer supporting surface effects movement thereof in a direction transverse to said latent image bearing surface and said development electrode comprises a screen.
 14. The electrostatographic machine as defined in claim 10 wherein the means for effecting movement of said developer supporting surface effects movement thereof in a direction longitudinal to said latent image bearing surface and said development electrode comprises a plurality of spaced parallel wires mounted in a direction transverse to the latent image bearing surface. 